It was this way before I started on as strong a painkiller as oxy. At the moment I take 80mg BD, Not sure what the absolute minimum needed to hold me is, I'd probably do OK with 60, and feel a bit rough, although manageably so at 40.
I don't see how the physical stuff going on could be psychosomatic either. My leg collapsed under me twice yesterday when I tried to walk on it. I'd got up off my bed,and as soon as I transferred my weight onto my bad leg, it folded under me, and did it again straight away as I tried to get up.
Luckily I wasn't hurt either time, but had to pull myself on top of my bed again with my upper body strength, and wait until my knee decided it was going to stay put.